1. Field of the Invention
This invention relates to devices which perforate conduits and more particularly it relates to devices which are capable of perforating a moving or advancing conduit.
2. Description of the Prior Art
In certain applications such as the drainage of water, it has been found advantageous to perforate the drainage tile along at least a portion of its length. The perforations allow the water to enter the tile, collect and eventually flow out of the end of the tile for ultimate disposal. To enable the water to freely flow, it is desirable to collect the water without causing sand, soil and the like to also enter into the interior of the tile.
One particular type of perforated tile specially adapted for the aforementioned collection and drainage of water, is described in U.S. Pat. No. 3,699,684 issued Oct. 24, 1972 and U.S. Pat. No. 3,830,373 issued Aug. 20, 1974 both to Marty E. Sixt. The plastic tile is corrugated, having alternating grooves and lands, and having openings selectively formed in the grooves to admit water into the tile. A screen is wrapped around the tile supported by the lands to prevent foreign materials, such as soil, from entering the tile.
To form the desired water admitting perforation in corrugated plastic drainage tiles and the like, various types of tools have been devised. One such device is shown in the Andrews U.S. Pat. No. 3,160,687 issued Dec. 8, 1964. The tile is drawn through the device wherein a rotating perforating roll, having a plurality of pins, punctures a wall of the tile. While this device does provide a means to perforate an advancing tile, such perforations are formed in only the one side of the tile which is engaged by the roll. No means are provided to easily adjust the size of the perforations created in the tile, and no means are provided to assure that, should corrugated tile be desired, only the grooves receive the perforation. Further, this type of device cannot be easily adapted to handle tiles of different diameters.
Another known type of device for perforating a tile is shown in the Zetzche U.S. Pat. No. 3,562,377 issued Feb. 9, 1971. The plastic tile partially wraps around and is advanced by the rotation of a sheave. Mounted on the sheave are orifice forming tools which advance and puncture the tile, pivot in a circulating motion creating circular bosses, and retract all in response to sheave rotation. This type of perforating device also encounters the same drawbacks discussed above.
Mechanical cutting of slits by rotary moving blades is known from U.S. Pat. No. 4,180,357.
It is the object of the present invention to set forth a tile perforating unit wherein the drawbacks outlined above are overcome.